The present application is concerned with scalable coding concepts such as scalable video coding.
Scalable coding concepts are known in the art. In video coding, for example, H.264 involves an SVC extension (Scalable Video Coding) allowing a base layer coded video data stream to be accompanied by additional enhancement layer data so as to increase the reconstruction quality of the base layer quality video in different terms, such as spatial resolution, signal-to-noise ratio (SNR) or the like. The recently finalized HEVC standard will also be extended by SVC profiles. HEVC differs from its predecessor H.264 in many aspects, such as, for example, suitability for parallel decoding/encoding and low delay transmission. As far as the parallel encoding/decoding is concerned, HEVC supports WPP (Wavefront Parallel Processing) encoding/decoding as well a tile parallel processing concept. According to the WPP concept, the individual pictures are segmented in a row-wise manner into substreams. The coding order within each substream is directed from left to right. The substreams have a decoding order defined thereamong which leads from the top substream to the bottom substream. The entropy coding of the substreams is performed using probability adaptation. The probability initialization is done for each substream individually or on the basis of a preliminarily adapted state of the probabilities used in entropy coding the immediately preceding substream up to a certain position from the left-hand edge of the preceding substream, respectively, on such as the end of the second CTB (Coded Tree Block). Spatial prediction does not need to be restricted. That is, spatial prediction may cross borders between immediately succeeding substreams. In this manner, such substreams may be encoded/decoded in parallel with the locations of current encoding/decoding forming a wavefront which runs, in a tilted manner leading from bottom left to top right, from left to right. According to the tile concept, the pictures are segmented into tiles and in order to render the encoding/decoding of these tiles a possible subject of parallel processing, spatial prediction across tile boundaries is prohibited. Merely in-loop filtering across tile boundaries may be allowed. In order to support low delay processing, the slice concept has been extended: slices are allowed to be switchable to either initialize the entropy probabilities anew, to adopt the entropy probabilities saved during processing a previous substream, i.e. a substream preceding the substream to which the current slice begin belongs, and to adopt the entropy probabilities having been continuously updated until the end of the immediately preceding slice. By this measure, WPP and tile concepts are rendered more suitable for low delay processing.
Nevertheless, it would be more favorable to have concepts at hand which further improve scalable coding concepts.